Multilayer Ceramic Electronic Component and Method for Manufacturing Same, as Well as Circuit Module, and Electronic Device

The present application claims priority to Japanese Patent Application No. 2024-056491, filed Mar. 29, 2024, the disclosure of which is incorporated herein by reference in its entirety including any and all particular combinations of the features disclosed therein.

The present disclosure relates to a multilayer ceramic electronic component and a method for manufacturing the same, as well as a circuit module, and an electronic device.

Multilayer ceramic electronic components such as multilayer ceramic capacitors (MLCCs) have been developed for installation in smartphones, personal computers, and various other electronic devices. The multilayer ceramic electronic components continue to see rising demands for size reduction and capacity increase as electronic devices become increasingly multi-functional/high in performance as well as large in battery capacity.

As for the capacity increase of ceramic electronic components, material compositions that increase the dielectric constants of dielectric materials used are being studied, while thickness reduction of dielectric layers and other measures are being taken. Meanwhile, making internal electrode layers thinner and thereby increasing the number of laminated layers is also an effective means. However, making the internal electrode layers thinner may present a problem of over-sintering, and consequently a lower continuity rate, of the internal electrode layers because the dielectric layers and internal electrode layers have different densification temperature ranges in the sintering stage. In such a case, connectivity between the internal electrode layers and external electrodes will drop, which in turn may prevent the desired properties from being achieved.

This has led to, for example, Patent Literature 1 that discloses a multilayer-type capacitor, comprising: a main body that comprises dielectric layers and internal electrodes placed alternately therewith; and external electrodes placed on the main body and connected to the internal electrodes; wherein, the internal electrodes comprise Ni crystal particles, a ceramic distributed inside the Ni crystal particles, first coating layers surrounding the Ni crystal particles, and second coating layers surrounding the ceramic; and the multilayer-type capacitor allows the internal electrodes to be made thin but subject to little thickness variation while also demonstrating excellent connection property because their outward growth is inhibited and also because the coated ceramic present inside the Ni crystal particles inhibits the Ni from moving and thereby inhibits spheroidization of the internal electrodes as well as disconnection of the internal electrodes.

Also, Patent Literature 2 discloses a ceramic electronic component, comprising: a multilayer chip formed in such a way that multiple dielectric layers whose main component is a ceramic are alternately laminated with multiple internal electrode layers whose main component is Ni, that it has a roughly rectangular parallelepiped shape, and that the multiple internal electrode layers are alternately exposed to two opposing end faces of the roughly rectangular parallelepiped shape; and external electrodes which are provided on the two end faces and whose main component is Ni; wherein, the multiple internal electrode layers contain an additive metal element other than Ni, as well as a co-existent material, and the concentration of the additive metal element is higher in the internal electrode layers than in the external electrodes; and the ceramic electronic component can maintain connectivity between the internal electrode layers and external electrodes.

With the conventional multilayer ceramic electronic components, a co-existent material is left in the internal electrode layers in order to delay the sintering of the internal electrode layers, so that an over-sintering of the internal electrode layers is inhibited even when they are sintered at the sintering temperature of the dielectric layers. This can inhibit the continuity rate of the internal electrode layers from dropping, thereby preventing a drop in the connectivity between the internal electrode layers and external electrodes. However, the co-existent material remaining in the internal electrode layers presents a problem of an increased resistance of the internal electrode layers and consequent drop in reliability.

An object of the present disclosure is to provide a multilayer ceramic electronic component, and a method for manufacturing multilayer ceramic electronic component, that can achieve an improved connectivity between the internal electrode layers and external electrodes along with an improved reliability.

An embodiment of the present disclosure is a multilayer ceramic electronic component, comprising: an element body having multiple dielectric layers laminated along a first axis and multiple internal electrode layers respectively placed along the first axis between the adjacent pairs of the dielectric layers; and a pair of external electrodes provided on the surface of the element body and electrically connected to the internal electrode layers; wherein, the dielectric layers contain a compound expressed by the general formula ABO(0≤α≤1) and having a perovskite structure wherein A and B represent an A-site element and a B-site element, respectively, of the perovskite structure; the internal electrode layers contain a first phase containing nickel and copper, as well as a co-existent material, and have, at the interfaces between the first phase and particles of the co-existent material, first segregation parts where copper has segregated; the concentration of copper in the first segregation parts is higher than the concentration of copper in the first phase; and the external electrodes contain nickel.

According to the present disclosure, a multilayer ceramic electronic component, and a method for manufacturing multilayer ceramic electronic component, that can achieve an improved connectivity between the internal electrode layers and external electrodes along with an improved reliability, can be provided. For purposes of summarizing aspects of the invention and the advantages achieved over the related art, certain objects and advantages of the invention are described in this disclosure. Of course, it is to be understood that not necessarily all such objects or advantages may be achieved in accordance with any particular embodiment of the invention. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein.

An embodiment of the present disclosure is explained in detail below. It should be noted that the embodiment is not limited by the following descriptions and can be modified as deemed appropriate to the extent that doing so does not deviate from the key points of the present disclosure. Unless otherwise stipulated, the “to” indicating a range of numerical values in this Specification carries a meaning that the numerical values shown before and after it are included in the range as the lower-limit value and the upper-limit value.

Additionally, in this Specification and the drawings attached hereto, those components that effectively have the same functional configuration s are sometimes denoted by the same symbols to omit redundant explanations. Also, in this Specification and the drawings attached hereto, the quantity, position, size, shape, etc., of each component are not limited to those in the embodiment of the present disclosure and may be changed to any desired quantity, position, size, shape, etc., in embodying the present disclosure. Additionally, the drawings show, as deemed appropriate, the X-axis, Y-axis, and Z-axis that are crossing with one another at right angles. The X-axis, Y-axis, and Z-axis specify a fixed coordinate system that is fixed for the multilayer ceramic capacitor representing an example of multilayer ceramic electronic component. When the outer shape of the multilayer ceramic capacitor representing an example of multilayer ceramic electronic component is a rough rectangular parallelepiped, the X-axis, Y-axis, and Z-axis can correspond to the length, width, and height of the multilayer ceramic capacitor.

The multilayer ceramic electronic component in this embodiment has: an element body having multiple dielectric layers laminated along a first axis and multiple internal electrode layers respectively placed along the first axis between the adjacent pairs of the dielectric layers; and a pair of external electrodes provided on the surface of the element body and electrically connected to the internal electrode layers. The multilayer ceramic electronic component in this embodiment may also have other layers or members if necessary.

is a perspective partial cross-sectional view illustrating the multilayer ceramic capacitorpertaining to an embodiment of the present disclosure.are cross-sectional views illustrating the multilayer ceramic capacitor.is a cross-sectional view illustrating a section cut along line A-A in.is a cross-sectional view illustrating a section cut along line B-B in.is an enlarged partial cross-sectional view of the dielectric layers, internal electrode layers, and second segregation parts of the element bodyinside region D in.

The multilayer ceramic capacitorcomprises an element bodyhaving a roughly rectangular parallelepiped shape, as well as a first external electrodeand a second external electrodeas a pair of external electrodes.

In the element body, the two opposing faces on its surface are referred to as the “upper face” and “lower face,” while the four faces that connect the upper face and lower face are referred to as the “side faces.” Normally the lower face represents, but is not limited to, the face on the board side when the multilayer ceramic capacitoris mounted on a circuit board. In the examples shown in, the element bodyis such that the first external electrodeand second external electrodeare provided on a first side faceand a second side face, respectively, which correspond to two opposing side faces. The first external electrodeextends from the first side faceonto the four adjoining faces. The second external electrodeextends from the second side faceonto the four adjoining faces. It should be noted, however, that the first external electrodeand second external electrodeare separated from each other. The external electrodes are not limited to being on the two opposing side faces, so long as they are provided on the surface of the element body.

The lamination direction in which dielectric layersand internal electrode layersare laminated is the first axis, and in, the first axis representing the lamination direction of the dielectric layersand internal electrode layerscorresponds to the Z-axis, being the direction in which the internal electrode layers are facing each other.

The axis orthogonal to the first axis representing the lamination direction is the second axis. In, the second axis, which is the axis orthogonal to the first axis representing the lamination direction, corresponds to the X-axis. The second axis runs along the length direction of the element bodyand is the axis running along the direction in which the first side faceand second side faceof the element bodyare facing each other, as well as the direction in which the first external electrodeand second external electrodeare facing each other.

The axis orthogonal to the first axis representing the lamination direction and also orthogonal to the second axis, is the third axis. The third axis is the axis that runs along the width of the internal electrode layers. In, the third axis, which is orthogonal to the first axis representing the lamination direction and also orthogonal to the second axis, corresponds to the Y-axis and is the axis running along the direction in which a third side faceand a fourth side facebeing the two side faces, besides the first side faceand second side face, of the four side faces of the element body, are facing each other (refer to). The X-axis, Y-axis, and Z-axis are mutually orthogonal.

The lamination direction is not limited to the Z-axis direction and may be any arbitrary direction. Accordingly, the first axis representing the lamination direction may be, for example, the X-axis corresponding to the X-direction or Y-axis corresponding to the Y-direction.

In the present application for patent, a drawing illustrating a specific embodiment may be used to explain general embodiments encompassing the specific embodiment; however, any subject matter explained based on the coordinate axis system used in an embodiment is applied correspondingly in general embodiments as being based on a general coordinate system in which the lamination direction is the first axis. For example, what are used inrepresenting a specific embodiment where the lamination direction corresponds to the Z-direction, and are explained as the X-axis, Y-axis, and Z-axis therein, can be applied correspondingly as the second axis, third axis, and first axis, respectively, in general embodiments.

The element bodyis constituted in such a way that dielectric layerscontaining a ceramic material that functions as a dielectric, and internal electrode layers, are laminated together alternately. The internal electrode layersinclude multiple first internal electrode layersand multiple second internal electrode layers. The first internal electrode layersand second internal electrode layersare laminated together alternately. The edges of the first internal electrode layersare extracted to the surface on which the first external electrodeis provided, or specifically first side facein the examples of, of the element body. The edges of the second internal electrode layersare extracted to the surface on which the second external electrodeis provided, or specifically second side facein the examples of, of the element body. This means that the first internal electrode layersand second internal electrode layersare electrically connected to the first external electrodeand second external electrodealternately. As a result, the multilayer ceramic capacitoris constituted as a laminate of capacitor units.

Also, the laminated body comprising the dielectric layersand internal electrode layersis such that internal electrode layersare placed as the outermost layers in the lamination direction, and the outer side faces in the lamination direction of the laminated body, or specifically upper face and lower face in the examples of, are covered with cover layers. The cover layershave a ceramic material as the main component. For example, the cover layersmay be identical to, or different from, the dielectric layersin terms of compositional makeup. It should be noted that the constitution is not limited to the one shown inso long as the first internal electrode layersand second internal electrode layersare exposed to different regions on the surface of the laminated body and electrically connected to different external electrodes. The “different regions on the surface of the laminated body” may be surface regions that are on opposing faces of the laminated body, respectively, or surface regions that are on adjoining faces of the laminated body, respectively, or surface regions that are different from each other on the same face of the laminated body. So long as they are separated from each other, the different external electrodes may extend onto other faces from the faces where the first internal electrode layersand second internal electrode layersare exposed to the surface regions of the laminated body, respectively.

Preferably the element bodyhas, at the interfaces between the dielectric layersand internal electrode layers, second segregation partswhere copper has segregated (refer to), the details of which are described later. In, the second segregation partsare not shown.

The size of the multilayer ceramic capacitoris not specifically limited, but it may be, for example, 0.25 mm in length, 0.125 mm in width, and 0.125 mm in height, or 0.4 mm in length, 0.2 mm in width, and 0.2 mm in height, or 0.6 mm in length, 0.3 mm in width, and 0.3 mm in height, or 1.0 mm in length, 0.5 mm in width, and 0.5 mm in height, or 3.2 mm in length, 1.6 mm in width, and 1.6 mm in height, or 4.5 mm in length, 3.2 mm in width, and 2.5 mm in height. It should be noted, however, that the sizes of the multilayer ceramic capacitorlisted above are only examples and the multilayer ceramic capacitoris not limited to the aforementioned sizes. The size of the multilayer ceramic capacitormay be one, for example, that satisfies the relationship of “length>width≥height,” or “width>length≥height,” or “height>length≥width,” or “height>width≥length.” It should be noted that, for example, the length represents the size in X-axis direction, width represents the size in Y-axis direction, and height represents the size in Z-axis direction.

As explained above, the multilayer ceramic capacitorin this embodiment has multiple dielectric layerslaminated along the Z-axis being the first axis, multiple internal electrode layersrespectively placed along the first axis between the adjacent pairs of dielectric layers, and a pair of external electrodesprovided on the surface of the element bodyand electrically connected to the internal electrode layers. The dielectric layers, internal electrode layers, second segregation parts, and external electrodesare explained below.

The dielectric layerscontain a compound expressed by the general formula ABO(0≤α≤1) and having a perovskite structure. The dielectric layersmay also contain additives if necessary.

The compound having a perovskite structure, if of a stoichiometric composition, is expressed by a general formula ABObecause a representing an amount deviating from a stoichiometric composition is 0. The compound having a perovskite structure and expressed by the general formula may be such that α is greater than 0 but no greater than 1. In other words, the compound having a perovskite structure and expressed by the general formula may be more oxygen-deficient than a stoichiometric composition.

In the general formula ABO, preferably “A” represents one or more types of elements selected from the group that consists of Ba (barium), Sr (strontium), Ca (calcium), and Mg (magnesium). In the general formula ABO, preferably “B” represents one or more types of elements selected from the group that consists of Ti (titanium), Zr (zirconium), and Hf (hafnium). In the compound expressed by the general formula ABOand having a perovskite structure, the elements “A” and “B” are respectively positioned at the A site and B site of the perovskite structure.

Specific examples of the compound having a perovskite structure include one or more types selected from the group that consists of barium titanate (BaTiO), calcium zirconate (CaZrO), calcium titanate (CaTiO), strontium titanate (SrTiO), magnesium titanate (MgTiO), and BaCaSrTiZrO(0≤x≤1, 0≤y≤1, 0≤z≤1) forming a perovskite structure.

BaCaSrTiZrOencompasses, for example, barium strontium titanate, barium calcium titanate, barium zirconate, barium zirconate titanate, calcium zirconate titanate, barium calcium zirconate titanate, and the like. It should be noted that, no matter which material it is, the compound having a perovskite structure may contain oxygen deficiency.

Preferably the dielectric layerscontain barium titanate, for its superior dielectric properties, as the compound having a perovskite structure, or it may contain barium titanate as the main component, or it may be constituted only by barium titanate. Barium titanate has excellent dielectric properties supported by extremely high relative dielectric constant, small dielectric loss, and the like. Accordingly, the capacitance of the multilayer ceramic capacitorcan be increased when its dielectric layerscontain barium titanate as the compound having a perovskite structure.

In this Specification, the “main component” refers to the component accounting for the largest amount, by atomic percentage of substance, of all components that are contained.

Also, in the dielectric layers, the compound having a perovskite structure may be contained as the main component. The dielectric layers, for example, may contain the compound having a perovskite structure by 50% by mol or more, or 90% by mol or more, or they may be constituted only by the compound having a perovskite structure.

The dielectric layerscan also contain additives as optional components.

The additives to be contained in the dielectric layersare not specifically limited and include, for example: oxides containing one or more types of elements selected from the group that consists of zirconium (Zr), magnesium (Mg), manganese (Mn), molybdenum (Mo), vanadium (V), chromium (Cr), and rare earth elements (scandium (Sc), cerium (Ce), neodymium (Nd), yttrium (Y), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), and ytterbium (Yb)); oxides containing one or more types of elements selected from the group that consists of cobalt (Co), nickel (Ni), lithium (Li), boron (B), sodium (Na), potassium (K), and silicon (Si); glasses containing one or more types of elements selected from the group that consists of cobalt, nickel, lithium, boron, sodium, potassium, and silicon; and the like.

The average dielectric layerthickness is not specifically limited, but it is preferably 1.0 μm or less, or more preferably 0.8 μm or less, or yet more preferably 0.5 μm or less, for example, from the viewpoint of making the multilayer ceramic capacitorsmaller while also increasing the number of laminated layers to allow for increase in capacitance. Also, the average dielectric layerthickness is preferably 0.2 μm or more, or more preferably 0.4 μm or more, for example, from the viewpoint of increasing the productivity and yield. The average dielectric layerthickness can be defined by any combination of a lower-limit value and an upper-limit value as deemed appropriate, and is preferably 0.2 μm or more but no more than 1.0 μm, or more preferably 0.2 μm or more but no more than 0.8 μm, or yet more preferably 0.4 μm or more but no more than 0.8 μm, or most preferably 0.4 μm or more but no more than 0.5 μm.

To evaluate the average dielectric layerthickness, the multilayer ceramic capacitoris polished along the Y-axis to prepare a sample that has been polished down to the center along the Y-axis to expose an XZ-plane in which the dielectric layersand internal electrode layersare laminated, as shown in. Within the exposed XZ-plane, two dielectric layerspositioned at the center along the Z-axis being the first axis are selected, and additionally two dielectric layerspositioned at the top edge, and two positioned at the bottom edge, along the Z-axis being the first axis are selected. In doing so, the dielectric layersto be selected are chosen from inside a capacitive part.

Then, each selected dielectric layeris measured for thickness at the center along the X-axis being the second axis, to obtain the thickness of the dielectric layer. The same procedure is followed to measure the thicknesses of all six selected dielectric layersto calculate the average value. This average value is defined as the average dielectric layerthickness in the multilayer ceramic capacitor. It should be noted that the dielectric layerthickness can be measured using a scanning electron microscope (SEM) or scanning transmission electron microscope (STEM). Since the dielectric layersand internal electrode layershave different compositional makeups, they are discriminated by differences in brightness when observed on electron beam images.

As illustrated in, the region where the first internal electrode layersconnected to the first external electrodeand second internal electrode layersconnected to the second external electrodeare facing one another represents a region of the multilayer ceramic capacitorwhere electrical capacitance is generated. Accordingly, this region where electrical capacitance is generated is referred to as the “capacitive part.” In other words, the capacitive partrepresents the region where each adjacent pair of the internal electrode layersconnected to the different external electrodesare facing each other.

The region where the first internal electrode layersconnected to the first external electrodeare facing one another in the lamination direction without the second internal electrode layersconnected to the second external electrodein between, is referred to as a “first end margin.” Also, the region where the second internal electrode layersconnected to the second external electrodeare facing one another in the lamination direction without the first internal electrode layersconnected to the first external electrodein between, is referred to as a “second end margin.” The first end marginand second end marginrepresent regions where the internal electrode layersconnected to the same external electrodeare facing one another in the lamination direction without the internal electrode layersconnected to the different external electrodein between. The first end marginand second end marginare regions where electrical capacitance is not generated.

Side marginsrepresent regions provided on the outer side of the capacitive partalong the third axis being orthogonal to the lamination direction and also orthogonal to the second axis, or in the direction along the Y-axis in the example of. In other words, the side marginsare regions adjoining, and on the outer side of, the capacitive partas viewed from the lamination direction, and regions adjoining, and on the outer side of, the capacitive parton the sides to which the internal electrode layersare not extracted. The side margins, too, are regions where electrical capacitance is not generated.

is an enlarged partial cross-sectional view of dielectrics layersand an internal electrode layer. The internal electrode layercomprises a first phasethat contains nickel (Ni) and copper (Cu), as well as a co-existent material, and has, at the interfaces between the first phaseand particles of the co-existent material, first segregation partswhere copper, being a metal added in the internal electrode layer, has segregated. The concentration of copper in the first segregation partsis higher than the concentration of copper in the first phase.

Preferably the first phasein the internal electrode layerscontains nickel as the main component for its excellent electrical properties and ability to reduce cost.

The content of copper in the first phasein the internal electrode layersis not specifically limited, but from the viewpoint of connectivity between the internal electrode layersand external electrodes, the content of copper relative to nickel is preferably 1 at % or higher but no higher than 11 at %, or more preferably 1 at % or higher but no higher than 6 at %. Also, the content of copper in the first phasein the internal electrode layersis preferably 1 at % or higher but no higher than 11 at %, or more preferably 3 at % or higher but no higher than 11 at %, based on the content of copper relative to nickel, from the viewpoint of reliability. Additionally, the content of copper in the first phasein the internal electrode layersis yet more preferably 3 at % or higher but no higher than 6 at %, based on the content of copper relative to nickel, from the overall viewpoint of connectivity between the internal electrode layersand external electrodesas well as reliability. It should be noted that the content of copper relative to nickel represents the atomic ratio of copper when that of nickel is 100 at %.

The first phasein the internal electrode layersmay contain, besides nickel and copper, other components generally used in the internal electrode layers of multilayer ceramic capacitors. Such other components generally used in the internal electrode layers of multilayer ceramic capacitors include, for example: tin (Sn) and other base metals or alloys containing the same; platinum (Pt), palladium (Pd), silver (Ag), gold (Au) and other noble metals or alloys containing the same; and the like. Any one type of these may be used alone, or two or more types may be combined.

A high content of other components besides nickel and copper in the first phasein the internal electrode layersmay make it difficult for the copper in the internal electrode layersto diffuse to the external electrodes, resulting in poor connectivity between the internal electrode layersand external electrodesas well as poor reliability. Accordingly, in the first phasein the internal electrode layers, the content of other components relative to nickel is preferably 0.5 at % or lower, or more preferably 0.1 at % or lower, or yet more preferably 0 at %. It should be noted that the content of other components relative to nickel represents the atomic ratio of other components when that of nickel is 100 at %.

The contents of nickel, copper, and other components in the first phasein the internal electrode layerscan be confirmed by performing an element analysis of the internal electrode layersusing any of various types of measuring equipment and calculating the atomic ratio of each component relative to all detected elements. Regarding the measuring equipment for element analysis, an energy dispersive X-ray spectrometer (EDS), wavelength dispersive X-ray spectrometer (WDS), electron probe micro analyzer (EPMA), laser ablation inductively coupled plasma mass spectrometer (LA-ICP-MS), or the like, installed on a scanning electron microscope (SEM) or scanning transmission electron microscope (STEM), can be used.